This type of doser-dispenser is described in Patent Application FR 89 06316 of 12.5.1989 and in Patent Application EP 90401252 of 15.5.1990 to which reference may be made for greater details.
In an installation for packing a liquid and/or pasty product in receptacles or recipients made by thermoforming a thermoplastic web, a plurality of juxtaposed doser-dispensers are used, in a row extending transversely with respect to the direction of advance of the thermoplastic web containing successive transverse rows of recipients parallel to that of that of the row of doser-dispensers and advancing step by step with the web in the direction of advance thereof.
These doser-dispensers are, like others (cf. for example French Patent 2 067 983), volumetric dosers which dispense determined quantities of product for a given product density. It frequently happens that the density of the product varies locally by some percent, with the result that the weight of the quantities of product dosed volumetrically and dispensed in the corresponding recipients differs beyond the allowed limits from the theoretical weight inscribed on said recipients. In order to eliminate the most important differences in weight, a filled recipient is weighed at regular intervals and its weight is compared with a standard recipient. When the difference in weight thus ascertained exceeds a limiting value, the stroke of the doser piston of each of the doserdispensers is readjusted as a function of the difference in weight. Such readjustment obviously requires that the whole installation be stopped, resulting in a loss of productivity.
In another installation disclosed in German Patent 3 510 110, the quantity dosed by the doser is checked from time to time, by diverting the dosed quantity from its normal discharge into a packaging recipient to a standard recipient disposed on precision scales whole output signal corresponding to the measured weight of said deviated dosed quantity is sent to the input of a computer such as a micro-processor. The signal corresponding to the measured weight of the dosed quantity is compared in this computer with a standard signal corresponding to a given weight. If there is a difference between the two signals, the computer emits a correction signal to modify the stroke of the piston of the doser in the sense of bringing the octal weight of the dosed quantity closer to the standard weight. During the process, the packaging recipients are not filled and transport of the recipients and actuation of all the other elements of the packing installation are stopped.
An object of the invention consists in eliminating or at least attenuating the drawbacks set forth and in proposing a doser-dispenser of the type initially mentioned, which does not require any stoppage of the installation for readjusting the quantities dosed by each of the doser-dispensers.